Bisfluorodinitro ethers and their preparation



US. Cl. 260-614 Claims ABSTRACT OF THE DISCLOSURE An energetic plasticizer bis(2-fluoro-2,2-dinitroethyl) ether is prepared by reacting a new stable intermediate bis(2,2rdinitro-3-hydroxypropyl) ether with a fluorinating agent in the presence of base.

CROSS REFERENCES TO RELATED APPLICATIONS This application is a continuation-in-part of copending application Ser. No. 605,129, filed on Dec. 21, 1968 and now abandoned, commonly assigned herewith.

BACKGROUND OF THE INVENTION This invention relates to the energetic plasticizer bis(2- fluoro-2,2-dinitroethyl) ether, its method of preparation and the intermediate compound bis(2,2-dinitro-3-hydroxypropyl) ether.

In the early years of explosive and propellant research, thermal stability was of relatively minor concern to the research chemist. At that time it was felt that an explosive which involved less than 2 cc. of gas per gram per hour in 48 hours at 100 C. in a vacuum stability test would withstand any vicissitudes of storage, handling or thermal environment in the applications envisaged. It soon became apparent however, that the development of more sophisticated weaponry would require a high energy explosive composition characterized by high thermal stability in the 150180 C. range and high detonation characteristics. In an effort to develop such an energetic composition, bis-(2-fluoro-2,2-dinitroethyl) formal (FEFO) was discovered and is the subject matter of application S.N. 173,- 592. filed Feb. 15, 1962 of common assignee herewith. FEFO suffered somewhat from a relatively high susceptibility to both acid and oxidative degradation due to the presence of the reactive formal linkage -OCH -O. In an effort to obviate these undesirable properties of FEFO, bis-(2-fluoro-2,2-dinitroethyl) ether was developed which unexpectedly was found to be not only less sensitive to chemical degradation, but also more dense, more ener getic and of an even higher thermal stability. The development of this composition is considered all the more surprising and significant because of the unobvious complex multistep process required for its preparation.

SUMMARY OF THE INVENTION It is therefore, an object of this invention to develop a new energetic plasticizer composition having specific application to explosives and propellants.

It is another object of this invention to provide an energetic composition possessing high thermal stability, low sensitivity to acid and oxidative degradation and high explosive properties.

It is a further object of this invention to provide a new and unobvious process for preparing the desired composition.

It is also an object of this invention to provide for a stable intermediate composition which is useful in obtaining the desired composition.

3,531,534 Patented Sept. 29, 1970 These and other objects are obtained by providing bis(2-fluoro-2,2-dinitroethyl) ether by the method of fluorinating bis(2,2-dinitro-3-hydroxypropyl) ether in the presence of a base.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Fluorination of bis(2,2-dinitro-33-hydroxypropyl) ether according to this invention may be affected by any known fluorinating agent including utilization of hydrogen fluoride in the presence of a suitable oxidizing agent, mercuric fluoride or other metallic fluorides such as cobalt triflnoride, silver difluoride, cerium tetrafluoride and manganese trifluoride. Preferable, however, is the utilization of elemental fluorine either along or diluted with an inert gas such as nitrogen, or the utilization of perchloryl fluoride.

It is desirable to fiuorinate in the presence of a base. While it is not intended for this invention to be bound by any theory of operation, it is generally believed that the base acts to remove the methylol group from bis(2,2- dinitro-3-hydroxypropyl) ether to form the anion thereby facilitating fluorination. For this purpose, any base is adequate; such as for example sodium hydroxide, sodium carbonate, potassium hydroxide, sodium bicarbonate, sodium acetate, ammonium hydroxide, which is representative and by no means exclusive. The desirable quantity of base required is dependent on the type used and the exact amount will be readily apparent to one of ordinary skill in the art.

During fluorination, it is desirable when using elemental fluorine or perchloryl fluoride as the fluorinating agent to maintain the bis(2,2-dinitro-3-hydroxypropyl) ether in solution. Any convenient solvent in which both the base and the fluorinating agent are at least partially soluble is adequate. As an example of suitable solvents there may be mentioned; acetonitrile, or water, when using fluorine, and dimethylformamide, lower alkanols such as methanol and aqueous lower alkanols when using perchloryl fluo ride.

The preferred procedure for carrying out this invention is to mix bis(2,2-dinitro-3-hydroxypropyl) ether with a solvent in the presence of a base.

The solution is then contacted with the fluorinating agent until slightly acidic and the original yellow color beings to disappear. More preferably, the said ether is fluorinated by utilization of fluorine diluted with nitrogen in a ratio of between 0.5 1.5 to 1.5 :0.5 fluorine to inert gas or by the utilization of gaseous perchloryl fluoride. In either case, the fluorinating agent is preferably, but not necessarily, introduced subsurface and passed through the solution until the bis(2-fluoro-2,2-dinitroethyl) ether is formed.

During fluorination, the solution is optimally maintained below room temperature and more preferably between 05 C., although temperatures ranging downward to the freezing point of the solution may be used. Obviously, however, such lower temperatures would affect the efflciency of the reaction. Higher temperatures may also be used so long as the reaction does not increase to an uncontrollable rate. The intermediate composition, bis(2,2-di nitro-3-hydroxypropy1) ether is also a novel and unobvious composition of matter produced according to this invention by the complex multi-step process which comprises reacting bis-Z-iodoethyl ether, prepared essentially as described by Gibson and Johnson (J. Chem. Soc., London, 1930, page 2526), with a dry ether suspension of silver nitrite. The resultant bis(Z-nitroethyl) ether is separated and dissolved in an aqueous basic solution. 0.1- 3.0 parts by Weight of this solution is then admixed with 3.0-0.1 parts by weight of a Formalin solution. 0.25-4 parts by weight of this solution is then reacted with 0.04 0.65 part sodium nitrite and 0.2-3.2 parts of silver nitrate. The resultant oily mixture comprises bis(2,2-dinitro- 3-hydroxypropyl) ether with (3-hydroxy-2-nitropropyl) (3-hydroxyl-2,2-dinitropropyl) ether as the major impurity which is present because the starting product is not fully nitrated. Separation of the products can then be accomplished by gas chromatography or fractional crystallization from a mixture of a chlorinated carbon solvent such as CC1 and a liquid hydrocarbon such as hexane. However, if desired, the oily mixture may be conveniently used without separation of the desired bis(2,2-dinitro-3- hydroxypropyl) ether which is fluorinated as described above.

In general, therefore, the synthesis of bis(2-fluoro-2,2- dinitroethyl) ether, involves a multistep process which may conveniently be illustrated by the followingschematic:

(1) OH (I) NaNOz (O2NC H2C H2) 20 The present invention can best be understood by one skilled in the art by reference to the following example, which is presented by way of illustration only and is not to be construed as limiting the invention.

Example Bis-2-iodoethyl ether was prepared essentially as described by Gibson and Johnson, J. Chem. Soc., London, 1930, 2526. Two hundred and eighty-five grams of freshly prepared, well dried, silver nitrite, was suspended in 600 ml. dry ether in a reaction flask protected from light and cooled to approximately C. With continued cooling (O5 C.), 250 g. bis-iodoethyl ether was added over a two hour period, the mixture was stirred 24 hours at the same temperature, allowed to warm to room temperature and stirred another 24 to 48 hours at ambient temperatures. The silver iodide was filtered off and washed with ether and the combined filtrates concentrated to give 120 g. crude bis-Z-nitroethyl ether. This material was purified by dissolving it at 0-5 C. in 500 ml. conc. sulfuric acid (addition time 0.5 hr.), stirring the solution for 15 min. at the same temperature and drowning it on crushed ice. The drowning liquors were extracted with five 200 ml. portions of methylene chloride. The extract was dried and freed from solvent to give 68 g. (54%) bis-2-nitroethyl ether.

The purity of the product was verified by vapor phase chromatography and infrared analysis (absence of nitrate ester band).

Bis-Z-nitroethyl ether, 50.75 g. was dissolved in an ice cold solution of 24.8 g. sodium hydroxide in 160 ml. water. 50.4 g. Formalin solution (36.3% formaldehyde) was added after the ether had dissolved completely and the mixture was stirred two hours at 0-5 C. Sodium nitrite, 42.7 g., was added, and when this was dissolved completely the solution was added rapidly with eflicient stirring and cooling (0-5 C.) to 211 g. silver nitrate in 240 ml. water. A black precipate formed immediately. The mixture was stirred 1.5 to 2 hours with ice cooling and filtered. Both filtrate and filtercake (after drying) were extracted exhaustively with ether, the extracts combined, dried and the solvent removed. The oily residue was digested with 500 ml. methylene chloride, the solution separated from the insoluble material and concentrated to give 50 g. of an oil which consisted mainly of a mixture of the methylol derivatives of trinitro and tetranitro diethyl ether.

35 grams of this mixture was added to 1 liter water in a fluorination apparatus consisting of a two liter three neck flask fitted with an efiicient stirrer, gas inlet tube and a coldfinger type trap on the outlet side of the system. The mixture was cooled to 05 C. and 35 g. sodium carbonate was added. After most of the oil had dissolved, fluorine diluted with nitrogen (1:1) was introduced subsurface with continued cooling until the pH of the mixture began to fall. Another 10 g. sodium carbonate was added and the fluorination continued until the solution was slightly acidic (pH 6-7) and the original yellow color of the solution was bleached.

The solution was acidified and exhaustively extracted with methylene chloride. After drying over magnesium sulfate the methylene chloride was removed and the residue fractionated by preparative gas chromatography and the main fraction was further purified by distillation in a molecular still at C./ 0.1 mm. 2 gm. of bis(2-fluoro- 2,2-dinitroethyl) ether was thus obtained.

Proof of structure for the material is based on the mode of formation, the infrared spectrum (bands characteristic for the fiuorodinitroethyl group at 810 and 855 CHIS-1, CO-C absorption at 11155 (AIL-1), elemental analyses (fluorine and nitrogen) and the NMR spectrum (doublet centered at 4.85 p.p.m., J 16.0 cps.).

The higher energy content of the bis-ether per unit weight is shown by comparing calculated heats of detonation of the ether and FEFO:

Cal./ g. FEFO 1260 Ether 1440 The higher thermal stability of the ether is evidenced by the smaller amount of decomposition gases evolved upon heating under standardized conditions:

After 2.5 hrs. heating at C. the amount of gas evolved in the next hour is: FEFO, 4.7 ml./g.; ether, 3.5 ml./g.;

After 3.5 hrs. heating the corresponding figures are: FEFO 8.3 ml./g.; ether, 3.6 m*l./g.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed and desired to be secured by Letters Patent of the Uni-ted States is:

1. Bis(2,2-dinitro-3-hydroxypropyl) ether.

2. Bis(2-fluoro-2,2-dinitroethyl) ether.

3. A mixture comprising bis(2,2-dinitro-3-hydroxypropyl) ether and (3-hydroxy-2-nitropropyl) (3-hydroxy-2, 2-dinitropropyl) ether.

4. A process for producing the composition of claim 2 which comprises contacting bis(2,2-dinitro-3-hydroxypropyl) ether with a fluorinating agent selected from the group consisting of fluorine gas, fluorine-inert gas mixture and perchloryl fluoride in the presence of a base selected from the group consisting of sodium hydroxide, sodium carbonate, potassium hydroxide, sodium bicarbonate, sodium acetate and ammonium hydroxide at a temperature below room temperature but above the freezing point of the solution.

5. The process of claim 4 wherein said gaseous mixture of fluorine and inert gas is present in a mole ratio of about 05:15 to 1.5:0.5 fluorine to inert gas.

6. The process of claim 4 wherein the bis(2,2-dinitro- 3-hydroxypropyl) ether is dissolved in a solvent selected from group consisting of dimethylformamide and lower alkanols.

7. A process for producing the composition of claim 2 which comprises:

admixing 0.1-3.0 parts by weight of an aqueous solution of the disodium salt of bis(2-nitroethyl) ether with 3.0-0.1 parts by weight of a Formalin solution to form a mixture;

reacting 0.25-4.0 parts by weight of said mixture with 0.04-0.65 part of NaNO and 0.2-3.2 parts AgNO to produce an oily mixture;

separating said oily mixture;

contacting said oily mixture with a fluorinating agent selected from the group consisting of fluorine gas, fluorine-inert gas mixture and perchloryl fluoride in the presence of a base selected from the group consisting of sodium hydroxide, sodium carbonate, potassium hydroxide, sodium bicarbonate, sodium acetate and ammonium hydroxide at 0-5" C.

8. The process of claim 7 wherein said oily mixture is placed in water and fluorinated by contacting with gaseous fluorine.

9. The process of producing the composition of claim 2 which comprises:

(a) reacting bis(2-iodoethyl) ether with a dry ether suspension of AgNO and separating the resultant bis(2-nitroethyl) ether;

(-b) dissolving the bis(2-nitroethyl) ether in an aqueous basic solution;

(c) admixing 0.1-3.0 parts by'weight of said basic solution formed in ('b) with 3.0-0.1 parts by weight of a Formalin solution;

20 (d) reacting 0.254.0 parts by weight of the solution formed in (c) with 0.040.65 part of NaNO; and 0.2-3.2 parts AgNO and separating the resultant oily mixture;

References Cited UNITED STATES PATENTS 3,296,313 1/1967 Frump 260-615 3,387,044 6/1968 Grakauskas et a1. 3,399,240 8/1968 Frankel.

FOREIGN PATENTS 190,878 3/ 1967 U.S.S.R.

HOWARD T. MARS, Primary Examiner US. Cl. X.R. 14988; 260615 

